Study On The Mechanical Characteristics And Failure Mechanism Of Stabilized Soil Mass By CDM

Thick soft soil layer tend limits the application of gravity structure in port engineering. Traditional methods of ground improvement handling poorly in terms of improving the bearing capacity of foundation. CDM has been widely applied in northern European countries, especially in Japan, for its excellent performance in improving bearing-capacity and few of pollution. But it has not been widely promoted in China, because of loss of construction equipment and experience and prices.First of all, failure models of CDM and checking method are concluded. Design and calculation theories of CDM are compared in Technical Specification for Offshore Cement Deep Mixing Technique to Consolidate Soft Soils in China, Cement Deep Mixing Method (CDM), Design and Construction Manual proposed by Cement Deep Mixing Method Association in Japan and Technical Standards and Commentaries of Port and Harbour Facilities in Japan.Two failure models of ground will happen in wall type improvement, which are the overall lateral failure model and the failure between walls. But there is no checking method in Chinese standard for checking the failure model between walls. In this paper, referring to the slip line in Prandtl’s solution, the continuity of slip line between passive zone and transition zone is supposed. Based on the slip line, slices method is applied to compute the bearing capability of composite ground. Furthermore, verification of the correctness of method in this paper is based on FLAC 3D. According to this method, a new method for checking the capability of wall type improvement is proposed.The block type improvement include floating type and fixed type. Linear distribution of foundation pressure is supposed in all standard in both China and Japan. But according to the results in this paper with FEM, except negligible stress concentration, the maximum of pressure occur in the interior zone of block, because of plasticity of strum and the relative stiffness between the block and the strum. Furthermore, the pressure under the wall type improvement and the axial force of long wall are smaller than the result computed according standard because of pile skin friction and pressure under the short wall, which are not considered. The discrepancy will increase when the floating wall type improvement is used.Furthermore, based on the practice, many ground improvements are compared, and stability against sliding in the rubble mound foundation is checked.